BIT 286: Web Applications Lecture 04 : Thursday, January 15, 2015 ASP.Net MVC - Models

First Steps With Model  first-mvc-app/adding-model.html first-mvc-app/adding-model.html  If you copy and paste the above you’ll get a 404 because of the newline after tutorials/ - delete the space (or the %20, once you’re looking at the 404) and try again.  Setting up the POCO / POJO, managed DB access  Custom connection (to LocalDB, but could be to elsewhere)  Scaffolding: Free CRUD!  Examining the index page 2

EF sets up your DB with “Code First”  “The Entity Framework (often referred to as EF) supports a development paradigm called Code First. Code First allows you to create model objects by writing simple classes. (These are also known as POCO classes, from "plain-old CLR objects.") You can then have the database created on the fly from your classes, which enables a very clean and rapid development workflow.” –Getting Started With MVCGetting Started With MVC  Database first is still an option 3

C# Class definition  Create a plain old CLR object (a normal class) in the Models folder public class Movie { private int numDoors = 4; public int GetNumDoors() { return numDoors; } public void SetNumDoors(int nD) { numDoors = nD; } public int ID { get; set; } public string Title { get; set { if( value == “”) throw new Exception(“blah”); else Title = value; } public DateTime ReleaseDate { get; set; } public string Genre { get; set; } public decimal Price { get; set; } }  These are C# Properties  “We'll use the Movie class to represent movies in a database. Each instance of a Movie object will correspond to a row within a database table, and each property of the Movie class will map to a column in the table.” 4

Scaffolding CRUD  CRUD =  Create  Read (examine individually, or list a bunch of them)  Update  Delete  In the Controllers folder, Add  Controller  MVC 6 Controller with views, using Entity Framework  Model Class: Movie  Data context class: ApplicationDBContext  “ Visual Studio creates the following files and folders:  A MoviesController.cs file in the Controllers folder.  A Views\Movies folder.  Create.cshtml, Delete.cshtml, Details.cshtml, Edit.cshtml, and Index.cshtml in the new Views\Movies folder. ” 5

Creating the Database  With luck, the directions behind the above link will work just fine  They didn’t work for me.  The problems were 1.The dnu/dnvm/dnx software wasn’t installed AND/OR 2.The dnu/dnvm/dnx software wasn’t added to the path  For an explanation about what dnu/dnvm/dnx are: Understanding-the-ASP-NET-Runtime Understanding-the-ASP-NET-Runtime 6

Creating the Database: Installing dnvm, etc  Run this to install dnvm (DotNet Version Manager): -NoProfile -ExecutionPolicy unrestricted - Command "&{$Branch='dev';iex ((new-object net.webclient).DownloadString(' ent.com/aspnet/Home/dev/dnvminstall.ps1'))}“  This will copy the files into C:\Users\ \.dnx\bin  Then cd to C:\Users\ \.dnx\bin so that you can use the dnvm program there. 7

Creating the Database: Installing dnvm, etc  Then run dnvm setup  If that doesn’t work try dnvm.cmd setup – it might not work without the.cmd extension  This seems to add the dnvm.cmd program to your path  If not, add it manually  This page has a good explanation – look for the “Via Control Panel” section This page has a good explanation  Add this to your PATH: C:\Users\ \.dnx\bin ; Don’t forget the ; - it’s what separates this entry from the next one  Skip the dnu restore, the do the remainder:  dnvm.cmd use rc1-update1 -p  dnx ef migrations add Initial  dnx ef database update 8

Take it for a spin   Index lists all the objects, in a nifty table  You can ‘Create New’ to add objects  This won’t add unless you get the date format exactly right (and there’s no feedback when you get it wrong  ) 1/1/2016 should work  For each object you can:  View details (a specific page with the same info, but bigger layout)  Edit the object  Delete the object  Ways to use this:  Consulting: generate pages to demonstrate basic stuff to the client  Start here, then go back and modify the HTML / etc so that it actually looks nice 9

Examining the Details page  The ViewData thing was convenient…  … but also error-prone  (there’s no way for the compiler to check that any given field will actually exist when executing the View)  A “Strongly typed” approach would be better  At compile-time we use an object from a specific class  Now compiler can check (in the View) if a given method/property actually exists 10

Examining the Details page public ActionResult Details(int? id) { if (id == null) { return HttpNotFound(); } Movie movie = _context.Movie.Single(m => m.ID == id); if (movie == null) { return HttpNotFound(); } return View(movie); } 11 This is like SELECT * FROM WHERE Note that we’re now passing this specific object to the View.

Examining the Details’ VIEW = "Details";} Details Name For(model => => model.Genre) 12 This will print out the field’s name. (In this case, ‘Genre’ This will print out the field’s value. (For example ‘Comedy’) This where we tell the view which C# type to expect

Examining the Details’ VIEW Name For(model => => model.Genre) 13 These are lambda expressions. Essentially they’re implied, local, “micro” functions.

Lambda Functions (Brief Overview) model => model.Genre  This is actually a very concise function definition.  You can think of this as saying something like: public string MyNewLambdaFnx(Movie model) { return model.Genre; }  UNLIKE a normal method, you can pass a lambda function as a parameter  (i.e., you can treat it kinda like data)  UNLIKE a normal method, these are ‘anonymous’  there’s no actual name for the function  More info at us/library/bb aspxhttps://msdn.microsoft.com/en- us/library/bb aspx 14

Examining the Index page public class MoviesController : Controller { private ApplicationDbContext _context; public MoviesController(ApplicationDbContext context) { _context = context; } // GET: Movies public IActionResult Index() { return View(_context.Movie.ToList()); } 15 This is like ‘SELECT *” This object connects to the database

Examining the Index page  In the controller file: public IActionResult Index() { return View(_context.Movie.ToList()); } In the view IEnumerable // Stuff left (var item in Model) => => item.Title) 16